Oxygen-vacancy-mediated electron localization at the nickel sites in nickel/iron layered double hydroxide towards efficient oxygen evolution reaction

Nickel/iron layered double hydroxide (NiFe-LDH) represents a promising electrocatalyst for the challenging oxygen evolution reaction (OER), yet the precise role of iron (Fe) in enhancing its activity remains unclear. Herein, we conduct a comprehensive investigation aimed at unraveling the influence of Fe incorporation on the atomic environments and electronic structure of NiFe-LDH, with the ultimate goal of establishing a correlation between these factors and elucidating the mechanisms by which Fe amplifies the OER performance. Our findings reveal that Fe dopants induce weakening of the nickel (Ni)-oxygen (O) coordination, and then generate abundant oxygen vacancies (O), which can mediate the electron transfer from Fe to Ni and finally result in electron localization at the Ni centers. The electron localization around Ni leads to the creation of a new energy level near the Fermi level and the formation of an electron-rich structure, resulting in a favorable electronic conductivity and reaction kinetics. The optimal NiFe-LDH sample exhibits an extraordinary electrocatalytic performance, requiring ultra-low overpotentials of only 189 and 248 mV to achieve current densities of 10 and 100 mA cm, respectively, in a 1.0 M KOH electrolyte. The comprehensive understanding obtained from this study can guide future design of high-performance NiFe-LDH-based electrocatalysts.